| I played bass back in my teens and young 20's; mainly metal; and used the one finger per fret method with no problem. I then put down bass for several years and just picked it up again a little less than 2 years ago.
Of course, I went right back to the one finger per fret method I had used before. Within two months, I was in so much pain, I couldn't stand to play more than just a few minutes. After talking with some instuctors, and my doctor, I had to change the way I played.
First, I had to stop playing for about 3 months; the last two were spent in physical therapy. Then, when I did start back up, I went to a fingering approach that, from what I understand, is more common on an upright bass. I don't use my ring finger at all anymore. I use my pinky for both the third and fourth frets in a four-fret spread.
This took a little getting used to, but I have had no pain at all since then. I'm now in a band and it is nothing for me to play 3-4 hours in a night with no discomfort at all.
My basic advise is: if it hurts, don't do it. The whole "no pain/no gain" business has no place in music. Get with a good instructor on the technique; check with your doctor on the pain. It main seem a little overkill, but you only have the two hands--mess them up and it's "game over".
Hope that helps.
--SmittyG | 
